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CROSSING ICE - Continued
Alluvial  Soil

Engineering Aid 3 - Beginning Structural engineering guide book
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CHAPTER  15 MATERIALS TESTING: SOIL AND CONCRETE In  previous  chapters  of  this  TRAMAN,  you studied the importance of many and various con- struction materials. However, one material that was  not  discussed  was  SOIL  which,  as  you  will learn in this chapter, is perhaps the most impor- tant material of all. Just as a poorly constructed and  weak  concrete  foundation  will  not  support a  building,  neither  will  a  poorly  “constructed” and weak soil, since the ultimate foundation for any road, airfield, building, or other structure is the natural earth upon which it is built. During this chapter you will learn what soil is. You will learn the different types of soil you might  encounter.  You  will  also  learn  the  basic properties  and  characteristics  of  soil  and  the importance  those  characteristics  play  in  deter- mining  the  adequacy  of  a  soil  for  use  as  a  con- struction  material.  In  addition,  you  will  learn  how to  collect  (sample)  soil  for  testing  purposes  and how to perform certain tests that you, as an EA3, will  be  responsible  for  performing.  Most  impor- tantly,  you  will  learn  why  those  tests  are  per- formed  and  their  importance  in  properly  and correctly  identifying  and  classifying  the  many types of soil that exist in nature. Finally,  this  chapter  begins  your  studies  of concrete  testing.  In  this  chapter  you  will  learn what the various tests are and the purpose and importance of those tests. You will learn how to perform  certain  tests  and  how  to  prepare  concrete samples for other tests that will be performed by more  senior  EAs. SOIL ORIGIN As   defined   by   Webster’s   New   World   Dic- tionary, soil is the surface layer of the Earth that supports  plant  life.  While  that  is  certainly  a correct definition and one that is perfectly satis- factory  to  many  groups  of  people,  it  lacks  the precision required by the civil engineer and soil technician. A more precise definition is that soil is a mixture of uncemented or loosely cemented mineral grains enclosing various sizes of voids that contain air (or other gases), water, organic mat- ter, or different combinations of these materials in  varying  amounts.  The  importance  of  under- standing  this  definition  will  become  obvious  as you progress through this chapter; but, first, let us  consider  where  soil  comes  from. SOIL  FORMATION The formation of soil is a continuous process that is still in action today. Basically, the Earth’s crust  consists  of  rock,  which  geologists  classify into  three  groups:  igneous,  which  is  formed  by cooling from a molten state; sedimentary, formed by  the  accumulation  and  cementing  of  existing particles and remains of plants and animals; and metamorphic,  formed  from  existing  rocks  that have been subjected to heat and pressure. When exposed   to   the   atmosphere,   this   rock   under- goes  a  physical  and  chemical  process  called WEATHERING,  which,  over  a  sufficient  length of  time,  disintegrates  and  decomposes  the  rock into a loose, incoherent mixture of gravel, sand, and finer material. It is this process that produces soils  of  various  designations. RESIDUAL  SOIL Any soil that results from weathering in place, and that is not moved during the weathering pro- cess,  is  called  a  RESIDUAL  soil.  A  mantle  of residual  soil  reflects  the  characteristics  of  the underlying  parent  rock  from  which  it  was  derived. TRANSPORTED  SOIL When  the  forces  of  nature  cause  the  mantle of soil to be moved to a place other than that of its  origin,  the  soil  becomes  a  TRANSPORTED soil. One of these soils often bears properties in- duced  by  its  mode  of  transportation.  The  chief agents of transportation are water, wind, ice, and the  force  of  gravity. 15-1







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